DE 10 2004 002 571 A1 shows a disk brake and a brake pad of the abovementioned type.
Disk brakes generally have brake pads guided and supported in pad wells on both sides of a brake disk, said brake pads being pressed against the brake disk by means of an application device arranged in the brake caliper during a braking process. In this case, the brake pad generally comprises a thick, flexurally stiff metal backplate as a pad support, which is produced as a casting or as a formed sheet-metal part and on which the friction lining is mounted. The stability of the backplate is intended to ensure that the friction lining is pressed against the brake disk uniformly and in full surface contact as far as possible. The dimensions of the backplate and the friction lining in the radial direction are such that they cover the friction strip of the brake disk in the radial direction.
The brake pad is supported and guided by means of its metal backplate in the respective pad well, which is formed on the brake support or the brake caliper.
The pad wells are delimited on the disk entry and disk exit side, i.e. in the circumferential direction, by supporting horns, on which the brake pads are supported under load by means of their side faces when they come into frictional contact with the brake disk, wherein the respective supporting horn subjected to load absorbs the braking torque acting on the associated brake pad.
Radially on the inside, the brake pads rest on supporting surfaces of the pad well, which are generally flat. Overall, the wells are generally of U-shaped design.
As regards their contours or as regards their dimensioning, the brake pad and the pad well are matched to one another in accordance with the embodiment/size of the brake. The supporting surfaces forming the U-shaped well, which can come into operative contact with the brake pad, are machined in the case of the component produced from cast material in which the well is formed, i.e. the brake caliper or the brake support, in order to ensure the required surface finish and the required dimensional accuracy.
In this machining process, the aim is, for reasons of economy in large-scale manufacture, to produce supporting surfaces which, as far as possible, can be obtained quickly, simply and without time-consuming tool changes. The supporting surfaces to be machined should therefore be level or smooth. In this case, machining operations with an end mill or a hobbing cutter, for example, are possible.
In the case of known disk brakes, e.g. according to DE 10 2004 002 571 A1, the well is generally rectangular, i.e. the legs of the “U” are at an angle of 90° (ignoring tolerances) to the “base” of the “U”. On the one hand, this embodiment simplifies machining. On the other hand, it is possible in this case for the brake pad to be inserted and removed in the radial direction through a corresponding installation opening in the brake caliper for the purpose of installation/removal. To ensure this, the well is rectangular, as already explained above. In other words, the distance between the two legs of the “U” is the same at the radially outer ends thereof as the distance at the radially inner ends thereof.
Particularly in the case of the pad well embodied as a rectangle, the brake pads must be secured against falling out by means of a hold-down system (springs/hold-down clip) of robust design secured on the brake caliper. Moreover, the hold-down system serves to compensate necessary functional clearances or tolerances.
Because of the limited space available for the brake, the radial extent of the lateral supporting horns is limited. It is therefore not possible for the lateral supporting surfaces formed thereon reliably to prevent the brake pad being twisted out during a braking process. As a result, the release behavior of the pad after a braking process may be impaired.
DE 694 03 650 T2 shows a pad support which tapers radially inward in plan view and is provided with lateral projections, which engage positively in lateral guide grooves of the pad well. Embodiments of this kind are known from relatively small disk brakes used in the passenger car sector. In this context, steel springs arranged in the guide grooves and serving to compensate bearing play are often used. The relatively small contact surfaces formed in this case cannot absorb the circumferential torques of the kind which arise with commercial vehicles. It would be uneconomic to enlarge the relevant surfaces to eliminate this problem because the production and machining of said surfaces would require special tools (form cutters) and a high outlay on conversion (machine/equipment). Moreover, the caliper of the brake according to DE 694 03 650 T2 does not have a radial opening for the installation/removal of the brake pads. The brake caliper must therefore be removed to install/remove the pad. Finally, it is also only possible to remove the brake pads from the positive engagement regions in an axial direction.